1. Field of the Invention
The present invention relates to a polarized semiconductor device, more particularly, which adopts a light guide structure with a principle similar to that of a photo crystal structure to relatively enhance effects of emitting specific polarized components.
2. Description of the Related Art
Recently, planar display technologies mainly about liquid crystal displays (LCDs) and plasma display panels (PDPs) have seen a rapid development. With a larger size in the display, a light source and optical materials account for a very significant proportion in costs. The large-sized display also causes the light source to consume considerable power.
Especially, in a liquid crystal display (LCD), a plurality of optical sheets should be adopted to ensure light to be diffused uniformly. This undermines light efficiency of a backlight unit (BLU) and increases manufacturing costs. In a method to overcome this problem, studies have been actively conducted on a method for utilizing a light emitting diode (LED) as the light source to enhance color reproducibility and response rate of the LCD.
FIG. 1 is an exploded view illustrating a conventional backlight unit employing an LED light source.
The backlight device of FIG. 1 includes the LED light source 2, a light guide plate 4, a diffusing sheet 5, a prism sheet unit composed of first and second prism sheets 6a and 6b, and a polarization plate 7.
As shown in FIGS. 2a and 2b, the LED light source 2 for general use in the backlight unit includes a light emitting structure having a first conductivity semiconductor layer 14 and 24, an active layer 16 and 26 and a second conductivity semiconductor layer 18 and 28 sequentially formed on a substrate 11 and 21, and first and second electrodes 19a and 19b; 29a and 29b electrically connected to the first and second conductivity semiconductor layers, respectively.
Light generated from the LED light source 2 propagates toward the diffusing sheet through the light guide plate 2. The light diffused by the diffusing sheet 5 is directed toward a liquid crystal panel (not illustrated) which is typically disposed above a protective sheet 17 through the first and second prism sheets 6a and 6b and the polarization plate 7.
Here, the diffusing sheet 5 ensures light to be emitted with uniform brightness onto an overall area, and the prism sheet unit 6 serves to enhance brightness of light within a specific view angle range. Also, the polarization plate 7 selectively transmits a specific polarized component. As described above, the backlight unit requires the various optical sheets to convert a point light source such as the LED into a bright and uniform surface light source across the screen.
Preferably, a specific optical sheet can be replaced with another conventional element such as the light source to reduce manufacturing costs, improve a manufacturing process of the backlight unit, and enhance light efficiency. Especially, a light source designed to selectively emit a specific polarized component can obviate a need for the polarization plate. This accordingly lowers costs attendant thereto and prevents light loss associated with selection of the polarized component. In this respect, the polarized light source can be very beneficially employed as the backlight light source.
However, in general, the LED light source 2 has polarized components in all directions, thereby necessitating a polarization plate for a desired polarized component. This consequently increases manufacturing costs and degrades light efficiency.